Placenta Accreta

In a normal pregnancy the placenta is supposed to attach itself to the inside wall of the uterus above or beside the fetus. Placenta accreta is an uncommon pregnancy condition that occurs when the attachment of the placenta into the uterine wall is too deep. The condition is medically classified as placenta accrete, placenta increta, or placenta percreta depending on the depth and severity of the placental attachment into the uterine wall. This is a relatively rare obstetric complication. Placenta accrete, increta, or percreta only occurs in 1 out of every 2,500 pregnancies.

Accreta, Increta, and Percreta

Placenta accreta, increta and percreta are sort of like degrees of severity (like 1st degree, 2nd degree, 3rd degree). Abnormal placental attachment is classified as accreta, increta, or percreta based on how deep the placenta goes into the wall of the uterus and who serious the situation is.

Placenta Accreta: accreta is like a 1st degree abnormal placental attachment. It occurs when the attachment of the placenta to the uterus is deeper than normal but not deep enough to actually penetrate the uterus muscle. Placenta accreta is the most frequent types of abnormal placenta attachment accounting for roughly 75% of all reported cases.

Placenta Increta: placenta increta is defined as a somewhat deeper (2nd degree) penetration of the placenta into the uterine wall. The wall of the uterus is almost fully penetrated but still falls short of attaching to the muscle. Increta is the second most common type of abnormal placenta attachment accounting for 15% of cases.

Placenta Percreta: placenta percreta is the most severe (3rd degree) type which occurs when the placenta completely penetrates through the uterine wall and muscle and attaches to another adjacent organ. Only 5% of cases are categorized as placenta percreta making it the least common form.

Causes of Placenta Accreta

The exact cause of placenta accreta is not fully understood. It happens somewhat spontaneously without warning. However, there are certain factors which are known to increase the risk of placenta accreta occurring. One of the primary risk factors associated with placenta accreta is placenta previa (a condition in which the placenta is abnormally positioned and covers the cervical entrance). 10% of placenta previa cases are further complicated by placenta accreta.

Prior history of C-section deliveries is also a well-known risk factor for placenta accreta. Women who have previously had C-sections are significantly more likely to have placenta accreta than those who have not. The more prior C-sections a woman has the greater her chances of developing placenta accreta will be. Over 60% of placenta accreta, increta, or percreta cases occur in women who have had more than 1 C-section and over 75% are in women with at least 1 prior C-section. Maternal age is also another risk factor. Mothers 35 years and older are more likely to have abnormal placental attachment.

Risks of Placenta Accreta

Placenta accreta is not always dangerous but it can often trigger complications that put babies at increased risk of harm. The most significant risk caused by placenta accreta is premature birth. Placenta accreta will often trigger premature labor and premature delivery of a baby. Babies born prematurely are at much higher risk for a host of birth injuries and health problems. Prematurity is really the primary risk to the baby associated with placenta accreta.

Placenta accreta can actually increase the risk of harm to mothers even more than their babies. Abnormal attachment of the placenta (particularly severe cases of placenta percreta) presents a very serious risk of maternal hemorrhage (internal bleeding) following delivery of the baby. Normally the placenta simply comes out after the baby, but with placenta accreta doctor must physically separate the placenta from the uterine wall. Detachment of the placenta following birth can be dangerous because it often results in severe hemorrhaging. This type of post-partum maternal hemorrhaging can be very dangerous because the blood may not clot correctly requiring an emergency blood transfusion.

With the most severe cases of placenta percreta (where the placenta punches through the uterus and attached to nearby organs) there is a risk of damage to those organs when detaching the placenta. Another common consequence of placenta accreta is irreparable damage to the uterus wall. This usually requires doctors to perform an emergency hysterectomy (surgical removal of the uterus) which means the mother will not be able to conceive any more children.

Prevention & Treatment

There is nothing that can be done to prevent or even predict placenta accreta. Although there are known factors which make it more likely to occur (prior C-sections, etc.) doctors have no way to tell in advance whether it is going to happen or not. They also have not method of decreasing the chances of it occurring.

There are also no real treatment options once placenta accreta occurs. Once placenta accreta is diagnosed all doctors can really do is closely monitor the condition and possibly schedule a preemptive cesarean-hysterectomy. This involves a C-section delivery followed by surgical removal of the uterus. This is safest way to handle placenta accreta because the hysterectomy prevents the risk of uncontrolled hemorrhaging that can occur when the placenta is detached from the uterus. For more severe cases of placenta precreta, a cesarean-hysterectomy is the only real option.